Shielded transmitter



Aug. 28, 1928. 1,682,409

A. NYMAN SHIELDED TRANSMITTER Filed Mar'ch 1 1924 WITNESSES: INVENTOR gig? Ward/Mew N5 man ATTORN E Y Patented Aug. 28, 1928.

UNITED STATES PATENT OFFICE.

ALEXANDER NYMAN, OF EAST ORANGE, NEW JERSEY, ASSIGNOB TO WESTINGHOUSE ELECTRIC 6n MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SHIELDED TRANSMITTER Application filed March 1,

My invention relates to sound sensitive devices and it has particular relation to transmitters of the shielded type.

Broadly speaking, the object of my invention is to provide means for a more accurate translation of sound wave vibrations into vi bratory electric currents.

More specifically, the object of my invention is to provide a combination of a microphone and sound reflecting and absorbing means which is adapted to respond fully to predetermined sound vibrations and respond to a much less degree to other sound vibrations.

In carrying my invention intoeflect, I provide a microphone in combination'with a metal sound-reflecting means and sound-absorbent means all combined with a supporting frame and stand, whereby sound from one direction is allowed free access to the microphone device, while sound from other directions is prevented'from influencing the microphone partly by being reflected away from the microphone, partly by being absorbed by absorbing means placed adjacent the microphone, and partly by abalancing of effects upon opposite sides of the microphone diaphragm.

In the translation of sound vibrations into vibratory electric currents for such pur-- poses as the radio broadcasting of entertainment, difliculty has been experienced in Ohtaining a satisfactory copy of the desired sound vibrations to the exclusion of other sounds. For such instances as those in which the desired sound comes exclusively from a single direction and the undesired sound comes exclusively from the reverse direction, it is possible, by my device, to obtain a translation of only the desired sound into vibratory electric currents and to exclude substantially all of the undesired sound.

I have found, by experiment, that sound waves striking a polished surface, such as a metal plate, at any other angle than that of 90 are substantially completely reflected. I have further found that by backing up such a reflecting surface with a felt pad, such waves as strike the reflector at a 90 angle and go through are absorbed. I have therefore provided, in my device a plurality of sound reflecting surfaces behind which are placed felt-absorbing means. I have placed these surfaces at an angle to each other, whereby sound which strikes the first one normal to its 1924. Serial No. 696,178.

surface, and therefore goes through, may strlke a second one at an angle other than 90 and thereby be reflected away.

Other objects and structural details of my invention will be apparent from the following description when read in connection with the accompanying drawing, wherein:

Figure 1 is a view in front elevation of my microphone device.

Fig. 2 is a view, partially in side elevation and partially in section, of the microphone of Fig. 1, and

Fig. 3 is a side elevational view of the microphonein its frame and stand. 7 In the figures, identical parts are designated by similar reference characters.

Referring to Figs. 1 and 2, asound'sensitiye microphone device 1, having projecting pms 2, 3, 4 and 5, is mounted in a supporting ring 6 through the agency of elastic cords 7, 8, 9 and 11, which are carried by hooks 12, 13, 14 and 15. v

To thering 6 are also attached a perforated sound-perviou's cover 16 and a sound-impervious shielding means 17. The sound-shielding means 17 consists of a erforated cylinder 18 to which is attached a flht plate 19.

Betwe'en'the microphone 1 and the plate 19 is mounted aflat disc of sound-absorbent ma terial 21. Attached to the outer surface of the disc 19 is a smooth cone 22. Between the disc 19 and the cone 22 is placed a filling of felt 23.

The cylinder 18 is held in place by screws 24, and the protective cover 16 is held in place by screws 25. Supporting hooks 26 and 27 are attached to cylinder 18, whereby the device can be suspended.

In Fig. 3, ring 6 and its attached devices are shown mounted upon a stand 28.

In the operation of my device, the side of microphone 1 covered by the perforated sound-pervious cover 16 is directed toward the source of sound to which it is desired that themicrophone respond, thereby simultaneously directing the other side of the microphone 1 and the various shielding means 22, 23, 17 and 21 towards other points from which undesired sounds may come.

In the event that undesired sound comes from a portion at one side of the device, it is free to enter the device through the perforations in both shield 16 and cylinder 18. The sound entering through the shield 16 then strikes the front of the diaphragm of microphone 1, and that entering through the perforation in the cylinder 18 strikes the back of the diaphragm. Since the distances to both sides from the source are practically equal, the sound waves are in phase, and they new tralize each other, producing no movement of the diaphragm, and they are not, therefore, translated into the output currents.

Under these conditions, the desired sound enters and influences microphone 1 freely, while the undesired sound is reflected away and thus prevented from influencing the microphone.

By this means, I am able to obtain a translation of the desired sounds into electrical vibrations, which translation is substantially free from interference produced by undesired sounds.

In practice, this makes it possible to broadcast a much more intelligible reproduction of such sounds as those produced by a public speaker, or other entertainer.

While I have shown only one embodiment of my invention in the accompanying draaing, it is capable of various changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be imposed thereon as are indicated in the prior art or in the appended claims. i

I claim as my invention:

1. A sound-responsive device comprisin in combination a microphone, a sound-shielding means and a. supporting means, said shielding means comprising a metal cone and a lining of sound-absorbing material.

2. A sound-responsive device comprising in combination a microphone, a sound-shielding means and a supporting means, said shielding means comprising a metal cone and sound-absorbing material, said sound-absorbing material being positioned between said microphone and said metal cone.

3. A sound-responsive device, comprising in combination a microphone, a sound-shielding means and a supporting means, said shielding means comprising a plurality of sound-reflecting surfaces and a plurality of sound-absorbent means, said reflecting surfaces comprising a metal cone and a metal plate, said sound-absorbent means comprising layers of felt adjacent to said reflecting surfaces.

4. A sound-responsive device, comprising in combination a microphone, a sound-shielding means and a supporting means, said shielding means comprising a plurality of sound-reflecting surfaces and a plurality of sound-absorbent means, said reflecting surfaces comprising a metal cone and a metal plate, said sound-absorbent means comprising layers of felt adjacent to said reflecting surfaces, said supporting means comprising a base, a standard extending therefrom, a ring carried by said standard, hooks on said ring and on said microphone, and elastic filaments co-operating with said hooks for supporting said microphone from said ring.

5. In a sound-responsive device, a microphone, enclosing means therefor, said enclosing means allordingready passage for sound on one side of the microphone and including a conical, sound-excluding shield on the other side thereof.

6. In combination, a disk-shaped microphone, an enclosing means therefor, said enclosing means having openings alfording ready passage for sound to one face of the microphone and to the periphery of the other face and means for preventing reflection of sound from the portion of the enclosing means adjacent said other face.

In testimony whereof, I have hereunto subscribed my name this 18th day of February,

ALEXANDER NYMAN. 

